Legionella Does Not Grow in Low-TOC Water

A test system supplied with different types of warm drinking water without disinfectant under controlled hydraulic conditions showed that treated aerobic groundwater (0.3 mg C per liter of organic carbon) induced a low biofilm concentration that supported no or very limited growth of L. pneumophila. Elevated biofilm concentrations and L. pneumophila colony counts were observed on surfaces exposed to two types of extensively-treated groundwater containing 1.8 and 7.9 mg C per liter and complying with the microbial water quality criteria during distribution. Control measures in the warm tap water installations therefore are essential for preventing growth of L. pneumophila.